Passive Sonobuoys from Sonobuoy TechSystems

Localization, or the precise determination of a submarine's location, course, and speed, is done with passive sonobuoys whenever possible. In the 1980's, when airborne US Navy searched for submarines, passive sonobuoys typically performed the majority of initial detections. Passive tactics are used because they deny a submarine the knowledge that a tracking aircraft is present. The 'A' size sonobuoys discussed below can be air-launched since they all employ a parachute to retard their descent and provide descent stability. They can also be hand-launched over the side of a ship. All employ a battery, which is energized upon saltwater contact. Once energized, a mechanism for inflating a float with CO2 gas is activated, suspending the sonobuoy. The sensors are then released to specified depths. Passive sonobuoys use hydrophones to convert underwater sound into electrical signals, which are amplified and frequency modulated for VHF transmission. Some sonobuoys have precision-calibrated hydrophones. Most sonobuoys automatically scuttle within 8 hours of deployment. Sonobuoys are typically shipped in a Sonobuoy Launch Container (SLC) that serves as the shipping, storage, and aircraft launch container or in a gray overpack for pneumatic or free-fall launch.

For the DIFAR sonobuoys (Directional Frequency Analysis and Recording), the main sensor is a hydrophone that has directional detection capabilities. The latest generation of DIFAR sonobuoys offers various sensor types, electronic selection and post-launch control.

AN/SSQ-53D DIFAR

The AN/SSQ-53D is the most widely used sensor internationally for all phases of ASW search and tracking. Basic capabilities include three hydrophone selections (90, 400 and 1000 feet), five life selections (0.5, 1, 2, 4 and 8 hours), DIFAR sensor, and the capability to set one VHF transmitter channel out of 99 available channels. The life, depth, and channels must be set using Electronic Function Selection (EFS) prior to launch.

AN/SSQ-53F DIFAR

The AN/SSQ-53F DIFAR is the latest directional passive sonobuoy being produced for the U.S. Navy. Basic capabilities include four hydrophone depth selections (90, 200, 400 and 1000 feet), five life selections (0.5, 1, 2, 4 and 8 hours), DIFAR, Constant Shallow Omni Sensor (CSO) or Calibrated Omni (CO), sensor selection capability, DIFAR AGC (Automatic Gain Control) On/Off and the capability to set one VHF transmitter channel out of 96 available channels. Depth, life, sensor, AGC, and channel selection may be set using Electronic Function Selection (EFS) prior to launch, and all but depth selection can be changed after deployment via Command Function Select (CFS). This sonobuoy automatically scuttles after 8 hours.
 Download ANSSQ-53F Data Sheet

 Download ANSSQ-77C Data Sheet

AN/SSQ-101 ADAR

The Air Deployed Active Receiver (ADAR) sonobuoy consists of a horizontal planar array of omnidirectional sensors. The sonobuoy is primarily used as a shallow water receiver for multi-static operations. This sonobuoy transmits for a minimum of 4.5 hours over an eight hour period. Switching the VHF transmitter off when active acoustic signals are not being transmitted in the water extends the period of operation. This sonobuoy has three selectable depths (65, 325, and 500 ft.). Depth and channel selection may be set via Electronic Function Selection (EFS) prior to launch, and channel selection can be changed and VHF transmitter power can be switched on and off after deployment via digital Command Function Select (CFS).
 Download AN/SSQ-101 ADAR Data Sheet